Energy Union (En Un) is a program released by the European Commission intended to create a single energy market between the European Union in order to have secure, affordable and sustainable energy. This way the imports will be reduced and the final price should be lower (theoretically) increasing the energy security for all the countries. The first communication was in February 2015 and is a very new topic for all the energy stakeholders in the EU. This is why a dissertation for the implications of this policy in UK was developed as part of the Master in Energy, Environmental Technology & Technology from City University London.UK is currently catalogued as an Energy Island (less than 10% of cross-border interconnection), with 30% of the generation based in coal, 30% in gas and 20% renewable, a liberalised market that varies with changes in gas or wind availability and the third highest kWh price from the EU. More than 20 energy policies and Conservative government with a constraint view against renewables’ subsidies. The implication for the UK and the En Un are divided into three: Infrastructural, Political and Economical. In the middle a map of the new cross-border grids proposed by this policy some of the findings are.The Energy Union in the UK will happen even if there’s no political wiliness or if they decide to not be part of the EU, mainly because the new infrastructure is already being developed (UK-Belgium) additional to the four current cross-border interconnectors. The wholesale market in UK is already liberalized and some cross border trades are being done with clean and cheap electricity from France and Holland; the key development is UK-Ireland, because UK, instead of being a 100% exporter to Ireland, will flip the coin with an import-export relationship with 8 interconnectors, electricity generated in Euros and close distance.Now it will not really matter if you generate electricity from Fossil Fuels, Nuclear or Renewable; the country will purchase from where is cheapest and available, independently from the source. Shale Gas, Nuclear, Gas and coal with CCS will be the important investment in the next years, not only in PPP (private public partnership) schemes but with R&D. New Universities courses will be develop (energy traders / brokers, cross border trade supervisors, etc) and more women should get involved. The £/ kWh for domestic and small companies will not be significantly reduced (albeit the low cost of it), those companies more engaged with the market will have very good deals and low £/ kWh.